Dock takes 5 minutes to show after startup

Hi Guys and thank you in advance.

Well, new 2019 iMac, Catalina already installed, and transferred files using Timemachine.

So let's set the scene. After the hour+ of transferring the files and when it finishes its all good, the dock shows up as normal and all my Adobe apps installed and the iMac restarted again... all is excellent. Now I then do the large update which took about 1 hour installing updates and what looks like restarting at points within the update - guessing security updates. It then starts up to the normal mac screen with desktop icons where they should be blah blah blah, but then I notice that the dock doesn't show up!

So my first go to is the system preferences. I check to see if its on auto hide, and its not. I then click auto hide to toggle it on and off, but still nothing. So i'm restarting, and going back to the system preferences (sp) and ticking it off... I then close the sp, and reopen sp, then there I see that its ticked back on. I do this many times.... then I left it alone for 5 mins and the dock popped up, and the auto hide in the sp is ticked off. So found bug 'number 1' remedy... just wait 5 mins, so not so bad.

The next thought is "I know, lets rename the dock preferences (com.apple.dock.plist) so it makes a new one", so I did that, restarted and... you guessed it... it didn't make a blind bit of difference.

Now nothing is different except the major update which made the dock take ages to come up.

So any guys out there with the same issue and hopefully a fix?

Background history: Worked with and fixed my own macs since 1995.